brazing

Pin Brazing is part of a technology developed in Sweden during the second half of the 20th century by AGA. The purpose, to bond current carrying cables to what was considered “Sensitive Substrate Materials”, or in this case Railroad Signal Bonding, Grounding and Pylon Grounding.

On railway tracks, the signal current originally passed through the rails and this required special contact connections at the rail junctions for continuity. Copper straps that become brittle after soldering and brazing were used, and in some cases still are. For many years, attaching them was a major concern among railway engineers. AGA’s pin brazing team solved the problem. The new method involved welding the cable lugs to the ends of the rail using an electromechanical gun to create an arc, but only for a very short time (about a second) and at such a low temperature that neither the copper nor the steel in the rail. It was damaged. Pin brazing is still used on railways both within and outside Europe.

In later years, the pin brazing process and products have been developed for use in the oil, gas, and utility industries as a safe method of connecting cables to pipelines. The most popular application is for cathodic protection purposes, including connection of cathodic protection system sacrificial anode cables, test pole cables, continuity bonding between pipeline sections, connection of monitoring cables, grounding and AC mitigation systems.

Pin brazing is basically ‘drawn arc silver brazing’, considered a brazing process and not (as is sometimes and incorrectly claimed by suppliers and even manufacturers) ‘electric arc silver soldering’, as that the working temperature or melting point of the filler material is below the base metal or substrate but above 800 degrees Fahrenheit (426.6 degrees Celsius). The filler metal, in the case of Pin Brazing, is a silver alloy typically consisting of Ag 55%, Cu 21%, Zn 22%, and Sn 2%, which when melted flows directly onto the closely fitting surfaces between the desired connection type and substrate material by capillary action.

Using a specially designed solder pin (the body of which is normally brass, or specialized stainless steel threaded studs can sometimes be produced, all of which are tipped with a specific portion of the above silver alloy and a flux material) . An automatic gun (similar in many ways to a stud welding gun, which acts as a means of completing a DC circuit through a manual switch and provides “lift” by using a small electromagnet to facilitate generation of an arc) and a power supply, the pin soldering process is known to be safe, fast, and reliable, requiring very little training.

Since portability has been an essential factor in the development of Pin Brazing, power is most commonly supplied by a portable rechargeable battery pack. These vary in size and weight in relation to the number of connections required. However, in cases where a virtually fixed power source can be provided, for example welding generators on board a pipe-laying vessel, many continuous connections can be made in a production environment. Timing is controlled electronically (when an electronic device is installed on a battery pack or generator) or by a fusible link located on the weld pin itself. Fuse-wire controlled systems, which due to the nature of the process and locality of common use (i.e. remote locations and extreme environments) have proven to be more successful as they require less attention in the field and present the end user with easy to operate and maintain electromechanical equipment.

Types of fittings vary between threaded stud connectors and direct connections. Threaded studs are popular where a temporary connection is required, they secure mechanically and require the specified wire to be connected to a crimp tab and then secured to the stud with a lock nut (wire-terminal-stud-substrate), but they are criticized due to their bulk and low electrical integrity. Direct connections are more permanent fixtures, historically made via a pin-solder compatible wire terminal, in which the required wire is crimped into the terminal and then the terminal is “pin-soldered” directly to the substrate (wire- cable terminal-substrate). However, the electrical and mechanical integrity of these has more recently been criticized as the main contender for similar connection types, they involve a Thermite process and can make ‘real’ direct (Cable-Substrate) connections.

Pin brazing solutions that produce cable substrate connections for railways have been available for some time, but in the pipeline industry they are sometimes impractical, requiring prefabricated cables with ‘integral eye’ connections, complex electronics and expensive or insubstantial direct pin soldering, often flimsy. systems that generate too much heat and could compromise the metallurgical integrity of the substrate. However, there are now two new systems that allow Cable-Substrate connections that meet all the required criteria of Cable-Substrate system products and greatly improve its shortcomings. The first is a product called Integra-Bond that combines the mechanical strength and versatility of a cable lug connection with the electrical integrity of the cable substrate and even a reduced heat affected zone (HAZ), the second is SABER, which is actually brazing with a shielded arc electrode. adaptation of the Integra-Bond system, greatly reducing negative metallurgical effects within the HAZ by preventing the drawn arc from coming into direct contact with the substrate material.

Due to the portability, ease of use, and versatility of a system that can be battery operated or in shop and offshore applications connected to a welding generator for continuous use, the pin welding system has become the ultimate solution for electrical bonding of sensitive substrates. materials around the world.